Enzymes used as laundry detergents have been continually improved since their commercialization in the 1970s. To date, protease, lipase, amylase, and cellulase have been developed for laundry detergents. Among these, protease has been the most widely used as an additive of laundry detergent. Widely used alkaline protease for laundry detergents exhibit their optimal activity at pHs 8 to 12 and at temperature of 40° C. to 60° C. Most proteases used as detergent enzymes are produced by the Bacillus species. They are classified as a serine protease and are widely known as subtilisin.
Subtilisin exhibits stability in high temperature but is not stable under certain conditions. Specifically, its activity is not maintained for a prolonged period upon exposure to urea, a protein denaturizing agent. Subtilisin also quickly and irreversibly loses its proteolytic activity at pH 4 or below. Moreover, the activity of subtilisin is weak at low temperature (15° C. to 25° C.). As such, it cannot be used effectively in Southeast Asia and Central and South America where people usually wash with low temperature water.
U.S. Pat. Nos. 5,741,694 and 5,482,849 describe subtilisin with biochemical properties altered through a site-directed mutagenesis. U.S. Pat. No. 5,401,657 describes bacteria which produce an alkali-resistant enzyme useful as a laundry detergent.
We isolated a vapk gene encoding a protease enzyme VapK, which can be advantageously used in laundry detergent in that it remains active at high temperature and at high alkaline pH, and is resistant to many surfactants and protein denaturants widely used in laundry detergents. The gene vapk has been cloned, sequenced and brought to expression in useful host cell. The gene vapk consists of 1,266 bp coding for 422 amino acids, and the molecular weight of the protease VapK is 27 kda. This enzyme is very resistant to various surfactants such as AOS or LAS and exhibits optimum activity at pH 10.5 and at the temperature of 50° C. Moreover, the protease VapK is more active at low temperatures than are commercially availiable enzymes.